The present invention relates to a pull-push switch for use as a power source switch or the like. More particularly, it relates to a pull-push switch in which a movable contact and a stationary contact are engaged and disengaged through an inverting spring by the pull-push operation of an operating shaft.
A known type of pull-push switch is shown in FIGS. 1 and 2.
In these figures, numeral 1 designates an insulating case constructed by upper and lower housing parts 1a and 1b each formed in the shape of an open box. The open portions of the housing parts are made to face one another to form a central open area for parts of the switch, and a metal frame 2 is provided for holding the housing parts together.
A lower wall portion of the case 1 is provided with a hole 1c, and a bearing 3 is supported adjacent the hole 1c by an adapter plate 4. An operating shaft 5 is disposed in the bearing 3 in a manner so that it may be freely pushed and pulled for axial movement. An engaging groove 5a for engaging inverting springs, to be described below, is provided in the peripheral surface of the fore end of the operating shaft 5. Shown at numeral 6 is an E-ring for holding the operating shaft 5 within the bearing.
Guide groove 1d extending parallel to the axis of the operating shaft 5 are respectively provided in the inner portions of opposing side walls of the insulating case 1, as shown clearly in FIG. 2. An actuator 7 formed of an insulating material into a generally U-shape is held in an inverted condition by the guide grooves 1d and can slide vertically within the insulating case 1. In the top part of the actuator 7 as viewed in FIG. 1, a pair of movable contacts 9, 9 are disposed through respective spring members 8, 8. In correspondence with the movable contacts 9, 9, a pair of stationary contacts 11, 11 are fixedly disposed on the upper wall portion of the insulating case 1. The stationary contacts 11, 11 are connected to terminals 11a, 11a respectively. Both of the movable contacts 9, 9 are electrically connected together by a path not shown, through the actuator 7. Thus, switch contacts are constructed of the movable contacts 9, 9 and the stationary contacts 11, 11.
The lower portions of the depending leg portions of the actuator 7 are provided with spring engaging holes 7a, 7a. A pair of inverting springs 12, 12 are formed generally as shown in FIG. 2 and have their crossed end portions within respective spring engaging holes, and are compressed between the spring engaging holes 7a, 7a and the engaging groove 5a of the operating shaft 5. As shown in FIG. 2, the inverting spring 12 is so formed that a linear spring member is bent into the shape of an isosceles triangle of small height. Both end parts 12a, 12a in a position corresponding to the vertex are inserted into the spring engaging hole 7a in an intersecting fashion. An engaging portion 12b corresponding to the base of the triangle is fitted in and engaged with the engaging groove 5a.
When the operating shaft 5 is pulled for axial movement away from the case 1, the end parts 12a of the inverting springs 12 move upward in FIG. 1, and the movable contacts 9, 9 come into contact with the stationary contacts 11, 11 respectively, so that the switch is set into the ON state (the state shown in FIG. 1). On the other hand, when the operating shaft 5 is pushed inwardly of the case 1, the inverting springs 12 are inverted in the direction opposite to the above, and the movable contacts 9, 9 move away from the stationary contacts 11, 11, so that the switch turns into the OFF state.
In accordance with the recent miniaturization of various electronic devices, the pull-push switch as above described has been required to be smaller in the outside dimensions.
In such prior-art pull-push switch, however, the insulating actuator 7 is disposed in the insulating case 1 in the manner to be movable in the same direction as the operating direction of the operating shaft 5, and the movable contacts 9, 9 are disposed in the actuator 7. Accordingly, the pull-push switch has the problem that the thickness of the insulating case 1 in the direction of the operating shaft 5 increases, so the miniaturization cannot be achieved satisfactorily.
The inverting spring 12 extended across the actuator 7 and the operating shaft 5 has both the end parts 12a, 12a inserted through the engaging hole 7a, and has the side of the engaging portion 12b fitted in and engaged with the engaging groove 5a of the operating shaft 5 in the compressed state. This leads to the problems that the assembling of the switch and the attendant fitting and engagement of the various paths are very troublesome, that a comparatively long time is taken for assembly, and that a high cost of the product is incurred.